1. Field of the Invention
The present invention relates to a valve slide with a slide housing and a slide passage opening. The slide passage opening is closable by means of a closing member which is slidable in the plane of the slide. A sealing surface is provided surrounding the slide passage opening. In the closed position of the closing member, a circumferentially closed sealing member whose shape corresponds to the sealing surface rests against the sealing surface and the imaginary straight generatrices of the sealing surface extend at a right angle to the plane in which the axis of the slide and the sliding direction of the closing member are located.
2. Description of the Related Art
Several types of construction of such valve slides are known. They are usually constructed as so-called wedge-type slides. The slides are called wedge-type slides because the cross-section of the closing member is wedge-shaped defining an acute angle. Valve slides of this type are very useful in many technical applications, especially where the requirements with respect to tightness are not very high.
A closing slide of the above-described type is disclosed in Austrian patent No. 352,491. The slide includes a wedge-shaped closing member which is enclosed with an elastic material. Slides of this type are used in water pipes. The wedge-shaped closing member is surrounded by a rubber-elastic envelope or coating which completely covers the closing member. This envelope or coating has a relatively great wall thickness. When the closing slide is closed, this thick-walled rubber member is forced by the closing member into the passage opening of the slide and the closing effect is ensured by the capability of this thick-walled rubber member to change its shape. This rubber member rests laterally against the wall of the passage opening of the greatest portion of its circumference. A flat, arc-like curved shoulder is provided in the upper portion of the passage opening. A part in the upper portion of the thick-walled rubber envelope projecting in axial direction of the passage opening rests on the shoulder when the slide is closed. Slides of this type are of very simple construction and can certainly perform the function for which they are intended in water pipes because, as already mentioned, the thick-walled rubber envelope is capable of changing its shape and can be pressed into the passage opening of the slide, so that the opening is tightly closed. Of course, such slides close tightly in water pipes. Slides of this type cannot be used in vacuum plants.
U.S. Pat. No. 3,565,393 discloses a plate-type slide which is used for closing a rectangular passage opening. A circumferential groove is provided in the cross-sectional plane of this passage opening in which the slide plate is moved. An elastic material for forming a sealing member is cast into the groove. A corresponding, slot-like recess is provided in the upper part of this sealing member for passing the plate-shaped closing member therethrough. A gap is provided between the wall of the groove and the cast, elastically deformable material. When the slide plate has been moved in, an excess pressure is built up in the gap by means of a pressurized gas or a pressurized liquid. The excess pressure presses the elastic material against the edges of the slide plate in order to ensure a sealing action of the plate in this manner.
Finally, the closing slide disclosed in German patent No. 33 90 493 should be mentioned. This closing slide is a slide of classical construction. When the slide is moved in and the components which perform the sealing action contact each other, the circumferentially closed sealing member which surrounds the passage opening is acted upon by a transverse load which acts in the plane of the sealing member and which squeezes the sealing member over the greatest portion of its circumference.
Constructions of this type cannot be used successfully in vacuum plants which is due to the particular type of load acting on the sealing member. When the closing member is moved into its closed position, from the moment when the sealing member touches the sealing surface and when the closing member is moved in further, a load acts on the greatest portion of the circumference of the sealing member transversely of the longitudinal direction. This load is a shearing load because the sealing member is fastened unilaterally on the closing member in some manner and the closing member moves during the closing procedure transversely of the sealing surface. If the sealing surface is uneven, even when this unevenness is microscopically small, the sealing member is damaged and the slide is no longer tight as required by vacuum technology. Microscopically small openings between the spaces to be sealed are already "holes" which may have a size which is a multiple of the size of gas molecules.
It is, therefore, the primary object of the present invention to further develop the known and proven valve slide construction in such a way that the load acts on the valve slide in a more favorable manner, i.e., the sealing member or its components are compressed only transversely of the axis thereof, or the sealing member or its components are stretched in the direction of the longitudinal axis thereof.